1. Field of the Invention
The present invention is directed to a method for the manufacture of a pn-junction having high dielectric strength and which extends essentially parallel to the boundary surface of a doped semiconductor body, the penetration depth approaching the boundary surface at its marginal edge.
2. Description of the Prior Art
There are known methods of the type herein involved wherein one or more field limiting ring structures are provided to surround the pn-junction and are diffused into the semiconductor body simultaneously with the pn-junction. These ring structures have a penetration depth which corresponds to that of the pn-junction. They are disconnected from external potentials during operation and act as voltage dividers, the division ratios being defined by their mutual spacing and the distance of the innermost ring structure from the pn-junction. The book by Blicher entitled "Thyristor Physics", Springer-Verlag 1976, pages 231-234 can be referred to in this respect. The disadvantage of such ring structures is that they require relatively large semiconductor surface in order to achieve high breakdown voltages and they are extremely sensitive to surface charges.